Fix an error in the type knot tying code.
Fix an error in the type knot tying code.

The new code is much simpler, too.  Some recursive struct type pattern
exposed some issues with a pattern match that was too strict in the
old code.  That has been replaced by a much simpler strategy to just
eagerly record visited types and defer anything visited to the knot
tying phase.

travitch/llvm-data-interop,travitch/llvm-data-interop